I'll add a little bit here, and it's one of those things that I believe I've acquired as I get older.
There is no shame in the words "I don't know." There is no shame in the words "I have no opinion on that."IMHO one of the bigger problems is that we think we know things we don't/can't know, or have opinions on things we don't/can't have enough information to form an informed opinion.
The problem with claiming to know things you don't truly know, or having opinions on things that you shouldn't, is that it can create a mental lock-in based upon what you think you know. That lock-in becomes part of the structure of our identity, and [as I've talked about elsewhere] many of our opinions/knowledge are actually just manifestations of our identity.
I want the scaffolding of my identity to be based as much as possible on things that I've had the time to study so I can claim I actually do "know" things about them, and/or to develop reasonably informed and logical opinions about. Anything beyond that I'd like to keep at arm's length so I don't infect my identity with bullshit.
What that often means is that I view a lot of the world with either skepticism or apathy.
- Skepticism: The assumption that everything I see, read, am told, etc, is guilty until proven innocent. This is especially true of anything that conforms to my worldview, because of the power of confirmation bias. If I actually want to decide whether I "know" something, I should be looking for all the possible flaws in the knowledge/argument, be looking for the counterarguments from multiple sources, etc. I try to accept as little as possible at face value. Where possible, I try to go to original source material rather than what people [incl. press] tell me the source material says/means.
- Apathy: There are times when a certain topic has had two sides so completely stake out positions that I don't believe I can accurately filter through the information necessary to "know" or have an opinion. Where I can't trust the information coming from either side, and don't have the ability to view primary source material or evaluate evidence directly. To avoid directly talking about current politics (as I no longer do that), I'll use the George Zimmerman / Trayvon Martin example. It was a massively politicized event, where only two people actually knew what happened, and one of them was dead. Yet EVERYONE thought they needed to dig into it and argue about it and have an opinion. For me, I realized that it had truly very little impact on my life, so I actively just didn't have an opinion. Don't try to argue it with me; I just don't care.
So this is a bit of a sideways to your actual question [which I intend to write more about], but I wanted to throw this out in the world and hope that maybe more people start picking it up.
You don't *HAVE* to know, or have an opinion on, everything. In fact, the world would be a better place IMHO of more of us had the humility to simply say "I don't know."